1. Field of the Invention
This invention relates to valve members and in particular to an automatic-lift type valve member for use in a slush or mud pump.
2. Description of the Prior Art
In the drilling industry, slush or mud pumps are utilized to circulate the drilling fluid or mud which counterbalances the pressure of oil, gas and the like. The drilling fluid generally comprises a suspension in water of fine-grained mineral matter such as cuttings from the drilling operation and may also include cottonseed hulls and chemical additives. Furthermore, depending upon the composition of the matter being drilled through, sand and gravel may be introduced into the drilling fluid and circulated therewith. Because of its composition of such elements, drilling fluid tends to be relatively abrasive.
One type of slush pump commonly used to circulate the drilling fluid comprises a reciprocating type pump with automatic-lift type suction and discharge valves. The conventional valves typically include an insert comprising a soft material such as neoprene, urethane or the like for mating with a valve seat in a sealing engagement. The insert is sandwiched between a metal body with guide fins extending upstream therefrom and a metal washer; the entire assembly being held together by a bolt.
Such slush pump valves have heretofore been accepted as the industry standard. However, such conventional slush pump valves frequently have problems in opening, closing and sealing. Due to the abrasive nature of the drilling fluid and the extreme operating pressures to which slush pumps are subjected, such conventional valves employed therein tend to fail prematurely. Such failures often occur when a piece of gravel or other matter becomes lodged between the seat and the insert whereby the valve member is prevented from fully closing and sealing such that drilling fluid is allowed to leak therepast. Due to the high pressure and abrasive characteristics of the drilling fluid, such leakage tends to rapidly erode the insert and cause a valve failure. Drilling operations must then be suspended until the failed valve can be replaced.
Yet another disadvantge of the conventional slush pump valves heretofore described is that the inserts thereof generally have the configuration of a flat washer, one face of which provides the only sealing surface of the valve member. Damage to this face may result in a leaky valve. Furthermore, since the sealing face of a conventional valve insert is oriented substantially normal to the direction of drilling fluid flow, it tends to somewhat impede the flow and be eroded thereby in a relatively short time.
A further disadvantage of such conventional slush pump valves relates to their relatively high cost due to the use of precision machined metal parts and a high labor content for assembly. Therefore, conventional slush pump valves tend to be relatively costly to manufacture, inefficient in operation and susceptible to premature failure.